Printed circuit boards are widely used to contain the electronic circuits of various products. Access to the components of these circuits for testing and repair while the printed circuit boards are installed in the product has presented a problem. Although it is possible to use automatic testing fixtures to analyze boards while they are not in the instrument, some problems are most easily ascertained while the board is in position in the product and in its normal operating mode. Also, when the unit malfunctions at a customer's site, service personnel cannot always rely on testing equipment as sophisticated as that available at manufacturing facilities.
Some previous printed circuit board mounting methods have employed rigid structures which provided limited access. They required the use of extender boards and extension cables to provide access to components on a selected board. These techniques frequently distort or interfere with the operation of the board which has been extended from its normal position.
Hinged stand-offs have been used to mount printed circuit boards to each other or a supporting structure. This type of system had the disadvantage that misalignment of the hinged stand-offs coupling a board to a supporting structure interfered with the proper operation of the hinges. Also, the removal of a board from a structure employing hinged stand-offs requires removing hardware coupling the board to be removed from other boards or the supporting structure above and below it.
According to the preferred embodiment of the present invention, interlocking hinges become an integral piece of the printed circuit board. These hinges then mate to form one contiguous structure. The one-piece hinges minimize fabrication and assembly costs since they can be plastic molded and do not require additional hardware.
The interlocking feature is provided by a projection and an opening on each hinge. In one position the projection on one hinge fits freely into the opening of a second hinge. In this position, it is easy to add additional boards to the stack or remove a particular board from the stack. But, when the hinges are rotated to the in-line position, a cam on the projection forms an interference fit with the opening and provides a rigid structure. Flexible cable is used to electrically couple the printed circuit boards.